This invention relates to lubricants for dynamic information storage members and, more particularly to the use of solid and liquid lubricants and the method of applying them to a record medium.
Magnetic record members, such as discs and tapes, are operated at extremely high speeds in data processing systems. A lubricant is either included in the magnetic recording medium or it is applied as a very thin layer over the recording medium to reduce friction and protect the surface against head contact.
In magnetic disc systems, the heads normally "fly" on an air film immediately above the magnetic surface. When the disc starts to rotate or when it is stopped, the low friction lubricating layer provides smooth head takeoffs and landings. Also, the low friction lubricating layer protects the recording medium against crashes caused by particles or debris on the disc and which may upset the flying characteristics of the head. Where the head contacts the magnetic surface before stability occurs, this contact should take place on a low friction layer which will restore stability faster and which will protect the fragile head and magnetic surface.
U.S. Pat. No. 3,862,860 Pardee et al describes solid lubricants including tetrafluoroethylene telomer for magnetic records. Solid lubricants have not been completely successful in data processing applications, such as magnetic discs, because the solid lubricating layer interferes with the sensitive magnetic transducing process and because the solid lubricant wears away in tracks under the head.
Liquid lubricants have been successfully used on magnetic records in data processing applications. For example, U.S. Pat. Nos. 3,778,308 Roller et al and 3,919,719 Wright et al describe the use of a liquid lubricant perfluoroalkylpolyether, which is sold under the trade name KRYTOX.RTM.. Such a liquid lubricant has the advantage that it will creep across the surface, thereby replenishing a portion of the layer which has been removed by abrasion or wear. At room temperatures, this liquid lubricant will protect the surface of the magnetic record for the desired lifetime. However, under higher operating temperatures, or long life applications the lubricant evaporates, thereby reducing the protection. The use of higher viscosity, longer chain molecules of perfluoroalkylpolyether prolongs the life of the lubricant because the evaporation rate is less. However, these higher viscosity lubricants sometimes cause the magnetic head to stick to the magnetic surface when stationary. Upon starting up, the head or recording surface may be torn.
It is an object of the present invention to obviate the disadvantages of prior art magnetic record lubricants by applying both solid and liquid lubricants.